Question

Can someone help with this one? Half life of 55Cr is about 2 hours. A sample of the isotopes delivered from the reactor to lab requires 12 hours. What is the minimum amount of material that should be shipped to get 1.0 mg of 55Cr.
I said 32mg but I got it wrong and I don't know why

Answer 1

You can use an equation or you could just do it intuitively; I choose to do this one intuitively.

1.0mg =12 hrs

2.0mg=10 hrs

4.0mg=8 hrs

8.0mg= 6hrs

16.0mg=4hrs

32.0mg=2hr

64.0mg=0hrs


So, you will initially need 64.0mg of 55Cr to have a minimum of 1.0mg after 12-hours.